Square–cube law

Abstract: Galileo was the first to postulate what has become known as the “square-cube law”. Its original intent was to better understand the biological limits of animals regarding their size. Observation showed that small animals were far superior to larger animals in their physical capabilities relative to their weights. This explains why a flea can jump many times its height and an elephant cannot get all four feet off of the ground at the same time. So, the flea is more efficient in this regard. Many airplane designers have taken notice of the square-cube law and use it to understand the practical limitations on aircraft size. In other words, why are there no airplanes 2X or 10X bigger than the largest transport? The answer is that the squarecube law puts a limit on airplane size. Does taking this one step farther and applying it to buoyant airships present the designer with similar size constraints? The answer is no. The paper discusses why this is so and how the design of airships has a different relationship to size compared to their aircraft cousins. This difference manifests itself in differing attitudes towards risk by project managers for airplane vs. airship programs. Programmatic risks associated with being overweight are quite different for airships compared to airplanes. Performance changes due to increased weight are also different.